Transmitter apparatus and multiantenna transmitter apparatus

ABSTRACT

A transmitter apparatus wherein a relatively simple structure is used to suppress burst errors without changing the block sizes of encoded blocks even when the number of modulation multi-values is increased. An encoding part subjects transport data to a block encoding process to form block encoded data. A modulating part modulates the block encoded data to form data symbols; and an arranging (interleaving) part arranges(interleaves) the block encoded data in such a manner that the intra-block encoded data of the encoded blocks, which include their respective single different data symbol, get together, and then supplies the arranged(interleaved) block encoded data to the modulating part. In this way, there can be provided a transmitter apparatus wherein a relatively simple structure is used to suppress burst errors without changing the block sizes of encoded blocks even when the number of modulation multi-values is increased.

This is a continuation of application Ser. No. 11/994,624 filed Jan. 3,2008, which is a 371 application of PCT/JP2006/313334 filed Jul. 4,2006, which is based on Japanese Application No. 2005-198177 filed Jul.6, 2005, the entire contents of each of which are incorporated byreference herein.

TECHNICAL FIELD

The present invention relates to a transmitting apparatus andmulti-antenna transmitting apparatus that encode transmit data using ablock code such as an LDPC (Low Density Parity Check) code, for example,and transmit that transmit data.

BACKGROUND

In radio communications, transmit data is generally encoded beforetransmission in order to improve error correction capability. Oneexample of such encoding is the use of an LDPC code such as described inNon-patent Document 1. This LDPC code enables error correction to beperformed using an extremely large block unit (constraint length), andis therefore considered to be resistant to burst errors and suitable forcommunications in a fading environment.

Also, a multi-antenna transmitting apparatus that transmits OFDM signalsfrom a plurality of antennas, such as described in Non-patent Document2, is known as a technology for improving data transmission speed. Withthis kind of multi-antenna transmitting apparatus, interleaving data inthe frequency direction (subcarrier direction) has been proposed as onemethod of suppressing burst errors due to frequency selective fading.

FIG. 1 shows an example of the frame configuration of a transmit signalin this kind of multi-antenna transmitting apparatus. In FIG. 1, apreamble for estimating distortion due to fading fluctuation—that is,channel estimation—and frequency offset between the transmitter andreceiver are placed at the head of a frame, followed by data symbols.Also, pilot symbols for estimating frequency offset that fluctuates overtime are placed in carrier Y. One square in FIG. 1 represents onesymbol. That is to say, in the example shown in FIG. 1, one OFDM symbolcomposed of a total of 7 symbols (data symbols and a pilot symbol) istransmitted at each of times i, i+1, . . . . At this time, data isinterleaved and placed in (1) (2) (3) . . . (11) (12) order within oneOFDM symbol.

-   Non-patent Document 1: “Low Density Parity Check Encoding and    Decoding Method, LDPC (Low Density Parity) Encoding/Sum-Product    Decoding Method” Triceps 2002-   Non-patent Document 2: “High Speed Physical Layer (PHY) in 5 GHz    band” IEEE802.11a 1999

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

When a block code such as LDPC code is used, as the number of modulationmulti-values increases, for example, the number of symbols fortransmitting one encoded block decreases, and one encoded block istransmitted in a shorter time. As a result, if there is a notch due tofading in this transmission period, a burst error is liable to occur.That is to say, the probability of a burst error increases as the numberof modulation multi-values increases.

With a block code such as LDPC code, the block size can be changed, andthe larger the block size (that is, the longer the constraint length),the smaller is the probability of a burst error due to a fading notch orthe like. Therefore, when the number of modulation multi-values isvaried as in the case of adaptive modulation, it is thought that bursterrors can be suppressed by increasing the encoded block size as thenumber of modulation multi-values increases.

However, designing an encoder so as to change the block size each timethe number of modulation multi-values is changed is not desirable due tothe complexity of the configuration of such an encoder.

Also, in MIMO (Multiple-Input Multiple-Output) or similar multi-antennatransmission, while high separation precision can be secured for a datasymbol immediately after the preamble placed at the head of a frame,enabling a high SNR to be obtained for a received signal, there has beena problem of separation precision declining with distance from thepreamble, resulting in a decrease in the SNR of the received signal.

It is an object of the present invention to provide a transmittingapparatus that enables burst errors to be suppressed with acomparatively simple configuration without changing the block size of anencoded block even when the number of modulation multi-values isincreased, and a multi-antenna transmitting apparatus that enablesdegradation of error rate performance due to distance from the preambleto be suppressed.

Modes for Solving the Problems

A transmitting apparatus of the present invention for solving the aboveproblem employs a configuration that includes an encoding section thatexecutes block encoding processing on transmit data and forms blockencoded data, a modulation section that modulates block encoded data andforms data symbols, an arranging (interleaving) section thatarranges(interleaves) block encoded data so that one data symbol iscomposed by collecting together intra-block data of different encodedblocks, and supplies the block encoded data to the modulation section,and a transmitting section that sequentially transmits data symbols.

A multi-antenna transmitting apparatus of the present inventiontransmits a preamble for signal separation simultaneously from aplurality of antennas and then transmits data symbols simultaneouslyfrom the plurality of antennas, and employs a configuration thatincludes an encoding section that executes block encoding processing ontransmit data and forms block encoded data, a modulation section thatmodulates block encoded data and forms data symbols, anarranging(interleaving) section that arranges(interleaves) block encodeddata so that one data symbol is composed by collecting togetherintra-block data of different encoded blocks, and supplies the blockencoded data to the modulation section, and a transmitting section thatsequentially transmits data symbols from the plurality of antennas.

Advantageous Effect of the Invention

According to the present invention, data in each encoded block areplaced discretely in a plurality of symbols, enabling a transmittingapparatus to be implemented that can suppress burst errors, and cansuppress degradation of error rate performance due to fading notches orthe like by means of a comparatively simple configuration withoutchanging the block size of encoded blocks, even when the number ofmodulation multi-values is increased.

Also, since the distance from the preamble can virtually be made uniformamong encoded blocks, a multi-antenna transmitting apparatus can beimplemented that can suppress degradation of error rate performance dueto the distance from the preamble.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a drawing showing an example of the frame configuration of atransmit signal of a conventional multi-antenna transmitting apparatus;

FIG. 2 is a block diagram showing the configuration of a transmittingapparatus according to Embodiment 1 of the present invention;

FIG. 3 is a drawing provided to explain LDPC encoding processing by anencoding section;

FIG. 4A is a drawing showing BPSK signal point arrangement, FIG. 4B is adrawing showing QPSK signal point arrangement, FIG. 4C is a drawingshowing 16 QAM signal point arrangement, and FIG. 4D is a drawingshowing 64 QAM signal point arrangement;

FIG. 5 is a drawing showing first assignment examples of symbols of LDPCencoded data by an arranging(interleaving) section, wherein FIG. 5A is adrawing showing bit assignment to each symbol in the case of BPSK, FIG.5B is a drawing showing bit assignment to each symbol in the case ofQPSK, FIG. 5C is a drawing showing bit assignment to each symbol in thecase of 16 QAM, and FIG. 5D is a drawing showing bit assignment to eachsymbol in the case of 64 QAM;

FIG. 6 is a drawing showing second assignment examples of symbols ofLDPC encoded data by an arranging(interleaving) section, wherein FIG. 6Ais a drawing showing bit assignment to each symbol in the case of BPSK,FIG. 6B is a drawing showing bit assignment to each symbol in the caseof QPSK, FIG. 6C is a drawing showing bit assignment to each symbol inthe case of 16 QAM, and FIG. 6D is a drawing showing bit assignment toeach symbol in the case of 64 QAM;

FIG. 7 is a drawing showing third assignment examples of symbols of LDPCencoded data by an arranging(interleaving) section, wherein FIG. 7A is adrawing showing bit assignment to each symbol in the case of BPSK, FIG.7B is a drawing showing bit assignment to each symbol in the case ofQPSK, FIG. 7C is a drawing showing bit assignment to each symbol in thecase of 16 QAM, and FIG. 7D is a drawing showing bit assignment to eachsymbol in the case of 64 QAM;

FIG. 8 is a drawing showing fourth assignment examples of symbols ofLDPC encoded data by an arranging(interleaving) section, wherein FIG. 8Ais a drawing showing bit assignment to each symbol in the case of BPSK,FIG. 8B is a drawing showing bit assignment to each symbol in the caseof QPSK, FIG. 8C is a drawing showing bit assignment to each symbol inthe case of 16 QAM, and FIG. 8D is a drawing showing bit assignment toeach symbol in the case of 64 QAM;

FIG. 9 is a block diagram showing the configuration of a multi-antennatransmitting apparatus of Embodiment 2;

FIG. 10 is a drawing showing an example of the frame configurations oftransmit signals of transmit signals transmitted from each antenna of amulti-antenna transmitting apparatus;

FIG. 11 is a block diagram showing the configuration of a multi-antennareceiving apparatus of Embodiment 2;

FIG. 12 is a drawing showing a model of communication between amulti-antenna transmitting apparatus and a multi-antenna receivingapparatus;

FIG. 13 is a block diagram showing the configuration of the signalprocessing section of a multi-antenna receiving apparatus;

FIG. 14 is a drawing showing the relationship between the SNRcharacteristics of a signal at different points in time in a receivingapparatus;

FIG. 15 is a drawing showing an example of arrangement(interleaving)processing of data after encoding;

FIG. 16 is a drawing showing an example of arrangement(interleaving)processing of data after encoding;

FIG. 17 is a block diagram showing another example of the configurationof a multi-antenna transmitting apparatus of Embodiment 2;

FIG. 18 is a drawing showing an example of arrangement(interleaving)processing of data after encoding;

FIG. 19 is a drawing showing an example of arrangement(interleaving)processing of data after encoding;

FIG. 20 is a drawing showing an example of arrangement(interleaving)processing of data after encoding;

FIG. 21 is a block diagram showing the configuration of a signalprocessing section;

FIG. 22 is a drawing showing an example of arrangement(interleaving)processing of LDPC encoded data;

FIG. 23 is a drawing showing an example of arrangement(interleaving)processing of LDPC encoded data;

FIG. 24 is a block diagram showing the configuration of a multi-antennatransmitting apparatus that performs adaptive modulation;

FIG. 25 is a block diagram showing the configuration of a multi-antennareceiving apparatus that receives an adaptive modulation signal;

FIG. 26 is a drawing provided to explain Embodiment 4, wherein FIG. 26Ais a drawing showing how the last block data is assigned when the numberof encoded blocks transmitted last is one, FIG. 26B is a drawing showinghow the last block data is assigned when the number of encoded blockstransmitted last is more than one and not more than two, and FIG. 26C isa drawing showing how the last block data is assigned when the number ofencoded blocks transmitted last is more than two;

FIG. 27 is a drawing provided, as an example for comparison, to explaindegradation of reception quality characteristics due to thecommunication conditions when a conventional encoded block assignmentmethod is applied, wherein FIG. 27A is a drawing showing the receivedfield strength state, FIG. 27B is a drawing showing an example of aframe configuration when the modulation method is BPSK, and FIG. 27C isa drawing showing an example of a frame configuration when themodulation method is 16 QAM; and

FIG. 28 is a block diagram showing configuration examples when thepresent invention is applied to a system that uses an eigenmode.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings.

Embodiment 1

FIG. 2 shows the configuration of a transmitting apparatus according toEmbodiment 1 of the present invention. In transmitting apparatus 10,transmit data S1 is input to an encoding section 11. Encoding section 11executes block encoding processing on transmit data S1, and sends blockencoded data S2 thus obtained to an arranging(interleaving) section 12.In this embodiment, encoding section 11 performs LDPC encodingprocessing.

Arranging(interleaving) section 12 arranges(interleaves) block encodeddata S2 so that one data symbol is composed by collecting togetherintra-block data of different encoded blocks, and suppliesarranged(interleaved) block encoded data S2 to a modulation section 15.Specifically, block encoded data S2 is input to a selector 13, and thatselector 13 sends block encoded data S2 in bit units to memories 14-1through 14-3 or modulation section 15. Memories 14-1 through 14-3function as buffer memories, and send temporarily stored bits tomodulation section 15 on a coordinated timing basis. For example, whenmodulation section 15 performs QPSK, memory 14-1 is used, and a bitstored in memory 14-1 is output at timing coordinated with a bit sentdirectly to modulation section 15 from selector 13. By this means, oneQPSK symbol is formed by modulation section 15 using a total of two bitscomprising a bit input from memory 14-1 and a bit input directly fromselector 13. On the other hand, when modulation section 15 performs 16QAM, memories 14-1 through 14-3 are used, and bits stored in memories14-1 through 14-3 are output at timing coordinated with a bit sentdirectly to modulation section 15 from selector 13. By this means, one16 QAM symbol is formed by modulation section 15 using a total of fourbits comprising bits input from memories 14-1 through 14-3 and a bitinput directly from selector 13.

To simplify the drawing, only three memories, 14-1 through 14-3, areshown in FIG. 2, but when modulation section 15 performs 64 QAM, fivememories are provided, and one 64 QAM symbol is formed by modulationsection 15 using a total of six bits comprising bits input from thesememories and a bit input directly from selector 13.

The configuration of arranging(interleaving) section 12 shown in FIG. 2is just one example, and any configuration may be used whereby blockencoded data S2 is arranged(interleaved) and supplied to modulationsection 15 so that encoded data in one block is assigned to a pluralityof data symbols.

Modulation section 15 performs adaptive modulation based on a controlsignal S10. That is to say, modulation section 15 switches itsmodulation processing among BPSK, QPSK, 16 QAM, and 64 QAM based oncontrol signal S10. Control signal S10 is also input to selector 13 ofarranging(interleaving) section 12, and selector 13 changes the bitarrangement(interleaving) rule according to which modulation processingis performed by modulation section 15. This will be explained in detaillater herein.

A transmit symbol S3 obtained by modulation section 15 is input to aradio section 16. Radio section 16 performs predetermined radioprocessing such as digital/analog conversion and up-conversion onmodulated symbol S3, and supplies an obtained RF signal S4 to an antenna17.

LDPC code generation processing by encoding section 11 of thisembodiment will now be described using FIG. 3. Encoding section (LDPCencoder) 11 has transmit data S1 (that is, data before LDPC encoding) asinput, and outputs block encoded data S2 (that is, data after LDPCencoding) by performing LDPC encoding on transmit data S1. For example,if data before LDPC encoding is designated (m1a, m2a, . . . , m490a),and the parity check matrix is designated G, (C1a, C2a, . . . , C980a)is output as data after LDPC encoding. That is to say, post-encodingblock #1 composed of 980 bits is formed from pre-encoding block #1composed of 490 bits.

Modulation processing by modulation section 15 will now be describedusing FIG. 4. As this modulation processing is a known technology, itwill be described briefly. FIG. 4A shows a BPSK signal pointarrangement, with one bit—that is, b1—transmitted in one symbol. FIG. 4Bshows a QPSK signal point arrangement, with two bits—that is, (b1,b2)—transmitted in one symbol. FIG. 4C shows a 16 QAM signal pointarrangement, with four bits—that is, (b1, b2, b3, b4)—transmitted in onesymbol. FIG. 4D shows a 64 QAM signal point arrangement, with sixbits—that is, (b1, b2, b3, b4, b5, b6)—transmitted in one symbol.

Arrangement(interleaving) processing by arranging(interleaving) section12, which is a characteristic of this embodiment, will now be describedusing FIG. 5 through FIG. 8. FIG. 5 through FIG. 8 show whichpost-modulation symbols bits in each LDPC encoded block are assigned to.Specifically, these drawings show the symbols in which encoded data inone block (data after LDPC encoding) composed of 980 bits are placed.The horizontal axis indicates the symbol time sequence, and the verticalaxis indicates the bit numbers composing one symbol—that is, b1 in thecase of BPSK; b1 and b2 in the case of QPSK; b1, b2, b3, and b4 in thecase of 16 QAM; and b1, b2, b3, b4, b5, and b6 in the case of 64 QAM.

In these drawings, #X-Y indicates the Y'th bit (bit number Y among 980bits) of the X'th encoded block. For example, #1-1 indicates the 1st bitof the 1st encoded block. Similarly, #3-979 indicates the 979th bit ofthe 3rd encoded block.

FIG. 5A shows bit assignment to each symbol when the modulation methodis BPSK. When the modulation method is BPSK, one bit (b1) is transmittedin one symbol, and therefore only one 980-bit encoded block istransmitted by means of 980 symbols.

FIG. 5B shows bit assignment to each symbol when the modulation methodis QPSK. When the modulation method is QPSK, two bits (b1, b2) aretransmitted in one symbol, and therefore two 980-bit post-encodingblocks are transmitted by means of 980 symbols. As is clear from thedrawing, each symbol here is composed by collecting together intra-blockencoded data of different encoded blocks. Specifically, bits #1-1through #1-980 of post-encoding block #1 are assigned to bit b1 of the980 QPSK symbols, and bits #2-1 through #2-980 of post-encoding block #2are assigned to bit b2 of the 980 symbols. By this means, bits (data) ineach encoded block can be dispersed temporally across a number ofsymbols equal to that of BPSK, enabling an overall drop in the qualityof data within an encoded block because of a notch due to fading to beavoided. Thus, since the probability of most data within an encodedblock being erroneous in a burst fashion is low, error rate performancecan be improved.

FIG. 5C shows bit assignment to each symbol when the modulation methodis 16 QAM. When the modulation method 16 QAM, four bits (b1, b2, b3, b4)are transmitted in one symbol, and therefore four 980-bit post-encodingblocks are transmitted by means of 980 symbols. A characteristic of bitassignment to each symbol here is that, as with QPSK, encoded data inone block is assigned to a plurality of symbols. Specifically, data #1-1through #1-980 of post-encoding block #1 are assigned to bit b1 of the980 16 QAM symbols, data #2-1 through #2-980 of post-encoding block #2are assigned to bit b2 of the 980 symbols, data #3-1 through #3-980 ofpost-encoding block #3 are assigned to bit b3 of the 980 symbols, anddata #4-1 through #4-980 of post-encoding block #4 are assigned to bitb4 of the 980 symbols. By this means, bits (data) in each encoded blockcan be dispersed temporally across a number of symbols equal to that ofBPSK, enabling an overall drop in the quality of data within an encodedblock because of a notch due to fading to be avoided. Thus, since theprobability of most data within an encoded block being erroneous in aburst fashion is low, error rate performance can be improved.

FIG. 5D shows bit assignment to each symbol when the modulation methodis 64 QAM. When the modulation method is 64 QAM, six bits (b1, b2, b3,b4, b5, b6) are transmitted in one symbol, and therefore six 980-bitpost-encoding blocks are transmitted by means of 980 symbols. Acharacteristic of bit assignment to each symbol here is that, as withQPSK and 16 QAM, encoded data in one block is assigned to a plurality ofsymbols. Specifically, data #1-1 through #1-980 of post-encoding block#1 are assigned to bit b1 of the 980 64 QAM symbols, data #2-1 through#2-980 of post-encoding block #2 are assigned to bit b2 of the 980symbols, data #3-1 through #3-980 of post-encoding block #3 are assignedto bit b3 of the 980 symbols, data #4-1 through #4-980 of post-encodingblock #4 are assigned to bit b4 of the 980 symbols, data #5-1 through#5-980 of post-encoding block #5 are assigned to bit b5 of the 980symbols, and data #6-1 through #6-980 of post-encoding block #6 areassigned to bit b6 of the 980 symbols.

By this means, bits (data) in each encoded block can be dispersedtemporally across a number of symbols equal to that of BPSK, enabling anoverall drop in the quality of data within an encoded block because of anotch due to fading to be avoided. Thus, since the probability of mostdata within an encoded block being erroneous in a burst fashion is low,error rate performance can be improved.

Second examples of arrangement(interleaving) processing ofarranging(interleaving) section 12 of this embodiment will now bedescribed using FIG. 6. The examples shown in FIG. 6 are similar tothose in FIG. 5 in that encoded data in one block is assigned to aplurality of symbols, and the same kind of effect can be obtained aswhen arrangement(interleaving) is performed as shown in FIG. 5. FIG. 6differs from FIG. 5 in that, with QPSK, 16 QAM, and 64 QAM, onepost-encoding block is not assigned to a fixed bit (for example, b1only), but is assigned to all bits (for example, in the case of 16 QAM,to b1, b2, b3, and b4). Specifically, when the modulation method is 16QAM, for example, a characteristic in this case is that block #1 istransmitted using b1, b2, b3, and b4, so that, for post-encoding block#1, data #1-1 is assigned to bit b1, #1-2 to b2, #1-3 to b3, and #1-4 tob4.

The reason for using this kind of assignment method will now beexplained. There are differences in 16 QAM b1 reception quality, b2reception quality, b3 reception quality, and b4 reception quality.Assume that b1 reception quality is the poorest. In this case, if block#1 is transmitted using only b1, block #1 will be the block with thepoorest reception quality. When packet communication is performed,packet errors are affected by the reception quality of the block withthe poorest reception quality. Therefore, in this case, receptionquality should be made uniform for blocks #1 through #4. Also,preferably, the number of times assignment is performed to b1, b2, b3,and b4 should be made as uniform as possible for blocks #1 through #4.The difference in the number of times assignment is performed shouldpreferably be once at most. Since the number of symbols is notnecessarily a multiple of 4 (bits) (the number of bits that can betransmitted in one symbol in 16 QAM), a difference of one time may occurhowever assignment is performed.

Here, a case in which 16 QAM is used has been described by way ofexample, but the same kind of effect can also be obtained when the samekind of processing is performed with 64 QAM. However, the same kind ofeffect cannot necessarily be obtained in the case of QPSK since there isno difference in reception quality between b1 and b2. Nevertheless,since the possibility of a difference in reception quality arising dueto distortion caused by the transmitting apparatus and receivingapparatus cannot be denied, there is a possibility of such an effectbeing obtained.

Third examples of arrangement(interleaving) processing ofarranging(interleaving) section 12 of this embodiment will now bedescribed using FIG. 7. The examples shown in FIG. 7 are similar tothose in FIG. 5 in that encoded data in one block is assigned to aplurality of symbols, and the same kind of effect can be obtained aswhen arrangement(interleaving) is performed as shown in FIG. 5. FIG. 7differs from FIG. 5 in that, while the same block data is transmitted bythe same symbols, the order of transmission is block #1 data and block#2 data blocks alternately for QPSK; block #1, block #2, block #3 inthat order for 16 QAM; and block #1, block #2, block #3, block #4, block#5, block #6 in that order for 64 QAM. That is to say, block data may beassigned to symbols at intervals instead of being assigned to successivesymbols as in FIG. 5. However, the kind of assignment methods shown inFIG. 5 and FIG. 6 enable intra-block data to be dispersed among moresymbols, and are therefore more effective in improving receptionquality.

Fourth examples of arrangement(interleaving) processing ofarranging(interleaving) section 12 of this embodiment will now bedescribed using FIG. 8. The examples shown in FIG. 8 are similar tothose in FIG. 5 in that encoded data in one block is assigned to aplurality of symbols, and the same kind of effect can be obtained aswhen arrangement(interleaving) is performed as shown in FIG. 5. Theexamples in FIG. 8 combine the concepts illustrated in FIG. 6 and FIG.7. In FIG. 8, symbols to which assignment is performed are changed in2-bit units. By this means, the same kind of effect can be obtained asin FIG. 5 and FIG. 6, but the kind of assignment methods shown in FIG. 5and FIG. 6 enable intra-block data to be dispersed among more symbols,and are therefore more effective in improving reception quality.

Thus, according to this embodiment, by providing an encoding section 11that executes block encoding processing on transmit data and forms blockencoded data, a modulation section 15 that modulates block encoded dataand forms data symbols, and an arranging(interleaving) section 12 thatarranges(interleaves) block encoded data so that one data symbol iscomposed by collecting together intra-block data of different encodedblocks, and supplies the arranged(interleaved) block encoded data tomodulation section 15, a transmitting apparatus 10 can be implementedthat enables burst errors to be suppressed with a comparatively simpleconfiguration without changing the block size of an encoded block evenwhen the number of modulation multi-values is increased.

The processing of arranging(interleaving) section 12 can be said to bearranging(interleaving) block encoded data so that one symbol iscomposed by collecting together block encoded data of more encodedblocks as the number of modulation multi-values of modulation section 15increases.

Embodiment 2

FIG. 9 shows the configuration of a multi-antenna transmitting apparatusof Embodiment 2 of the present invention.

Multi-antenna transmitting apparatus 100 is a transmitting apparatusthat performs so-called OFDM-MIMO communication, and transmits differentmodulated signals from two antennas. Specifically, multi-antennatransmitting apparatus 100 transmits a modulated signal A from anantenna 114A and transmits a modulated signal B from an antenna 114B. InFIG. 9, virtually the same configuration is used for the signalprocessing system for modulated signal A and the signal processingsystem for modulated signal B, and therefore “A” is appended toreference codes for the modulated signal A signal processing system, and“B” is appended to reference codes for the corresponding modulatedsignal B signal processing system.

A frame configuration signal generation section 115 of multi-antennatransmitting apparatus 100 outputs a control signal 116 with frameconfiguration related information, encoding method information,modulation method information, and so forth. An encoding section 102Ahas modulated signal A data 101A and control signal 116 as input,executes encoding based on control signal 116, and outputs post-encodingdata 103A.

An arranging(interleaving) section 104A has post-encoding data 103A andcontrol signal 116 as input, arranges(interleaves) post-encoding data103A based on control signal 116, and outputspost-arrangement(interleaving) data 105A.

A modulation section 106A has post-arrangement(interleaving) data 105Aand control signal 116 as input, executes BPSK, QPSK, 16 QAM, or 64 QAMmodulation based on control signal 116, and outputs a baseband signal107A.

A serial/parallel conversion section (S/P) 108A has baseband signal 107Aas input, executes serial/parallel conversion, and outputs a parallelsignal 109A. An inverse Fourier transform section (ifft) 110A hasparallel signal 109A as input, executes a Fourier transform, and outputsa post-Fourier-transform signal 111A—that is, an OFDM signal. A radiosection 112A has post-Fourier-transform signal 111A as input, and formsa modulated signal A transmit signal 113A by executing predeterminedradio processing such as frequency conversion and amplification.Transmit signal 113A is output as a radio wave from antenna 114A.

The same kind of processing is also executed for modulated signal B bymeans of an encoding section 102B, arranging(interleaving) section 104B,modulation section 106B, serial/parallel conversion section (S/P) 108B,inverse Fourier transform section (ifft) 110B, and radio section 112B,and a modulated signal B transmit signal 113B is transmitted as a radiowave from antenna 114B.

FIG. 10 shows an example of the frame configurations of transmit signalsof modulated signal A and modulated signal B transmitted from antennas114A and 114B of multi-antenna transmitting apparatus 100. FIG. 10Ashows a frame configuration of modulated signal A transmitted fromantenna 114A, and FIG. 10B shows a frame configuration of modulatedsignal B transmitted from antenna 114B, in this embodiment, spatialmultiplexing MIMO (Multiple-Input Multiple-Output) transmission is usedas the communication method, and therefore modulated signal A andmodulated signal B symbols of the same carrier and the same time aretransmitted simultaneously from different antennas, and multiplexedspatially.

The preamble placed at the head of a frame is for estimating channelfluctuation. A receiver estimates channel fluctuation using thepreamble, and can separate modulated signal A and modulated signal Busing ZF (Zero Forcing) or MMSE (Minimum Mean Square Error) processing.

Pilot symbols placed in the time direction of carrier Y are symbols usedby a receiving apparatus to estimate and eliminate frequency offset thatcannot be eliminated by means of the preamble and distortion(amplitude/phase) due to device characteristics.

Data symbols are symbols for transmitting data, and are transmittedafter the preamble.

FIG. 11 shows the configuration of a multi-antenna receiving apparatusthat receives and demodulates a signal transmitted from multi-antennatransmitting apparatus 100.

A radio section 303_1 of a multi-antenna receiving apparatus 300 has areceived signal 302_1 received by an antenna 301_1 as input, executesamplification, frequency conversion, and so forth, and outputs abaseband signal 304_1. A Fourier transform section (fft) 305_1 hasbaseband signal 304_1 as input, executes a Fourier transform, andoutputs a post-Fourier-transform signal 306_1.

A modulated signal A channel fluctuation estimation section 307_1 haspost-Fourier-transform signal 306_1 as input, extracts the modulatedsignal A preamble shown in FIG. 10A, estimates modulated signal Achannel fluctuation based on this preamble, and outputs a modulatedsignal A channel fluctuation estimation signal 308_1.

A modulated signal B channel fluctuation estimation section 309_1 haspost-Fourier-transform signal 306_1 as input, extracts the modulatedsignal B preamble shown in FIG. 10B, estimates modulated signal Bchannel fluctuation based on this preamble, and outputs a modulatedsignal B channel fluctuation estimation signal 310_1.

A radio section 303_2, Fourier transform section 305_2, modulated signalA channel fluctuation estimation section 307_2, and modulated signal Bchannel fluctuation estimation section 309_2 operate in the same way asdescribed above.

A signal processing section 311 has post-Fourier-transform signals 306_1and 306_2, modulated signal A channel fluctuation estimation signals308_1 and 308_2, and modulated signal B channel fluctuation estimationsignals 310_1 and 310_2 as input, and obtains modulated signal A receivedata 312A and modulated signal B receive data 312B by performing ZF(Zero Forcing), MMSE (Minimum Mean Square Error), or suchlikeprocessing, and also performing decoding. The operation of signalprocessing section 311 will be described in detail later herein usingFIG. 13.

FIG. 12 shows a model of communication between a multi-antennatransmitting apparatus and a multi-antenna receiving apparatus. Here, amodulated signal transmitted from an antenna 409A is designated Txa(t),and a modulated signal transmitted from an antenna 409B is designatedTxb(t) (t: time). Also, if channel fluctuations between the respectivetransmitting and receiving antennas are designated h11(t), h12(t),h21(t), and h22(t), a received signal received by an antenna 401_1 isdesignated R×1(t), and a received signal received by an antenna 401_2 isdesignated R×2(t), the following relational expression holds true.

$\begin{matrix}{\begin{pmatrix}{{Rx}\; 1(t)} \\{{Rx}\; 2(t)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(t)} & {h\; 21(t)} \\{h\; 12(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}{{Txa}(t)} \\{{Txb}(t)}\end{pmatrix}}} & (1)\end{matrix}$

FIG. 13 shows the configuration of signal processing section 311 ofmulti-antenna receiving apparatus 300. A separation/frequency offsetestimation/compensation section 401 has post-Fourier-transform signals306_1 and 306_2, modulated signal A channel fluctuation estimationsignals 308_1 and 308_2, and modulated signal B channel fluctuationestimation signals 310_1 and 310_2 as input, and separates modulatedsignal A and modulated signal B by performing Equation (1) inversematrix computation (ZF). Also, separation/frequency offsetestimation/compensation section 401 estimates frequency offset anddistortion (amplitude/phase) due to device performance using the pilotsymbols shown in FIG. 10, compensates for these based on the estimationresults, and obtains a modulated signal A post-compensation basebandsignal 402A and a modulated signal B post-compensation baseband signal402B.

A soft decision calculation section 403A has modulated signal Apost-compensation baseband signal 402A as input, and obtains a softdecision value 404A by calculating a branch metric. A deinterleavingsection 405A has soft decision value 404A as input, and obtains apost-deinterleaving soft decision value 406A by performingdeinterleaving (the reverse of the processing performed byarranging(interleaving) section 104A). A decoder 407A haspost-deinterleaving soft decision value 406A as input, and obtainsmodulated signal A receive data 408A by decoding thispost-deinterleaving soft decision value 406A.

A soft decision calculation section 403B, deinterleaving section 405B,and decoder 407B perform the same kind of operations as described above,and obtain modulated signal B receive data 408B.

FIG. 14 shows an example of the relationship between the signal to noisepower ratios (SNRs) of carriers 1 through 6 at times i+1, i+2, i+3, i+4,and i+5, obtained in a receiving apparatus. As shown in FIG. 14, the SNRof a data symbol falls with temporal distance from the preamble. This isbecause the frequency estimation error and the estimation error ofdistortion (amplitude/phase) due to device characteristics in thereceiving apparatus increase with temporal distance from the preamble.

When interleaving is performed within one OFDM symbol and deinterleavingis performed by the receiving apparatus, as in FIG. 28 for example, databelonging to an OFDM symbol temporally distant from the preamble, suchas at times i+4 and i+5, is composed of only data symbols with adegraded SNR in consideration of the phenomenon in FIG. 14, even thoughinterleaving is executed, and therefore it is difficult to obtain codinggain even though error correction is performed, and error rateperformance degrade.

In a conventional system in which the transmitting and receivingapparatuses each have only one antenna, this problem can be solved veryeasily. It is only necessary to insert symbols for frequency offset anddistortion estimation, such as pilot symbols for example. In this case,pilot symbols need not be inserted so frequently, and therefore the dropin transmission speed due to pilot symbol insertion is small, and pilotsymbol insertion is not such a major disadvantage for the system.

On the other hand, in a multi-antenna system such as a MIMO system thatuses spatial multiplexing, separation symbols (comprising the preamblein FIG. 10) for separating modulated signals mixed on the transmissionpath are essential. Also, channel fluctuations h11 through h22 areestimated using these separation symbols, and causes of degradation ofthe estimation precision of channel fluctuations h11 through h22 includetemporal fluctuation of frequency offset and distortion. However, theabove-described drop in SNR cannot be prevented simply by insertingpilot symbols and estimating temporal fluctuation of frequency offsetand distortion estimation. In the final analysis, the above-describeddrop in SNR cannot be prevented unless the estimation precision ofchannel fluctuations h11 through h22 is ensured. A possible method ofachieving this is to increase the frequency of separation symbolinsertion. That is to say, a solution is difficult even if the frequencyof pilot symbol insertion is increased. However, since it is necessaryfor separation symbols to be placed in all carriers, there is a problemof transmission speed falling significantly if the frequency ofseparation symbol insertion is increased. It is therefore important toimprove the SNR while keeping the frequency of separation symbolinsertion as low as possible.

In this embodiment, a multi-antenna transmitting apparatus is proposedthat enables degradation of the error rate performance of data placed ina symbol distant from the preamble to be suppressed without increasingthe frequency of preamble insertion.

In this embodiment, the above-described problem is solved by acontrivance of the arrangement(interleaving) processing ofarranging(interleaving) sections 104A and 104B provided between encodingsections 102A and 102B and modulation sections 106A and 106B. This willnow be explained in detail.

Here, arranging(interleaving) sections 104A and 104B performarrangement(interleaving) so that input m'th data is placed in a datasymbol at the carrier p(m) position on the frequency axis, and in a datasymbol at the time q(m) position on the time axis. Thisarrangement(interleaving) processing is expressed as π(m)=(p(m),q(m)).

FIG. 15 and FIG. 16 show examples of arrangement(interleaving)processing of data after encoding by arranging(interleaving) sections104A and 104B. By way of illustration, FIG. 15 and FIG. 16 show examplesin which data arrangement(interleaving) is performed within six OFDMsymbols. The preambles are omitted. In FIG. 15 and FIG. 16, (1), (2),(3), . . . indicate the order of data placement, meaning, for example,that the data input first is placed in data symbol (1), and the datainput second is placed in data symbol (2).

The important point in the arrangement(interleaving) shown in FIG. 15and FIG. 16 is that the 1st data and 2nd data are placed in data symbolpositions of different times. For example, when encoding sections 102Aand 102B execute block encoding processing for a block size of 6,arranging(interleaving) sections 104A and 104B assign the six data itemsin an encoded block to symbols at temporally different positions. Thus,for example, data after block encoding is assigned to symbols so thatq(1)≠q(2)≠q(3)≠q(4)≠q(5)≠(6) and q(7)≠q(8)≠q(9)≠q(10)≠q(11)≠q(12).

By this means, it no longer happens that data with a degraded SNR arepositioned consecutively in a data sequence on which the receivingapparatus has performed deinterleaving, and therefore coding gain can beobtained by performing error correction, and degradation of error rateperformance can be suppressed.

Taking SNR correlativity in the frequency axis direction intoconsideration (SNR correlativity being higher between close carriers),degradation of error rate performance can be further suppressed byarranging(interleaving) encoded data so that, in addition to the aboveconditions, p(1)≠p(2)≠p(3)≠p(4)≠p(5)≠p(6) andp(7)≠p(8)≠p(9)≠p(10)≠p(11)≠p(12).

Thus, according to this embodiment, by providing arranging(interleaving)sections 104A and 104B that arrange(interleave) encoded data so thatencoded data within the same encoded block is assigned to a plurality ofdata symbols in the time direction, it is possible to prevent all datawithin an encoded block from being assigned to data symbols at positionsdistant from the preamble. In other words, distances from the preamblecan be made virtually uniform among encoded blocks, making it possibleto implement a multi-antenna transmitting apparatus 100 that enablesdegradation of error rate performance due to distance from the preambleto be suppressed. In addition, the influence of notches due to fadingcan also be reduced.

In the description of this embodiment, a frame configuration composed ofonly a preamble, data symbols, and pilot symbols, such as shown in FIG.10, has been taken as an example, but the frame configuration is notlimited to this case, and symbols that transmit control information, forexample, may also be included. In short, this embodiment is suitable forapplication to a wide range of cases in which data symbols are precededby a preamble.

In the configuration example in FIG. 9, a configuration is illustratedin which encoding sections 102A and 102B are provided respectively formodulated signals A and B, but this embodiment can also be applied to aconfiguration in which encoding processing of both modulated signals Aand B is performed by one encoding section.

FIG. 17 shows an example of such a configuration. In FIG. 17, in whichparts corresponding to those in FIG. 9 are assigned the same referencecodes as in FIG. 9, encoding section 102 and arranging(interleaving)section 104 in multi-antenna transmitting apparatus 500 are the onlypoints of difference from multi-antenna transmitting apparatus 100.

Encoding section 102 has data 101 and control signal 116 as input,executes encoding based on control signal 116, and outputs post-encodingdata 103. Arranging(interleaving) section 104 has post-encoding data 103and control signal 116 as input, arranges(interleaves) post-encodingdata 103 based on frame configuration information contained in controlsignal 116, and supplies post-arrangement(interleaving) data 105A and105B to modulation sections 106A and 106B respectively.

FIG. 18, FIG. 19, and FIG. 20 show examples of arrangement(interleaving)processing of data after encoding by arranging(interleaving) section104.

In FIG. 18, 6-bit data after encoding is first assigned to modulatedsignal A data symbols of different times (corresponding to (1), (2),(3), (4), (5), (6) in FIG. 18). Then 6-bit data after encoding isassigned to modulated signal B data symbols of different times(corresponding to (7), (8), (9), (10), (11),(12) in FIG. 18). Next,6-bit data after encoding is assigned to modulated signal A. In thisway, data after encoding is assigned to data symbols of different times,and is assigned alternately to modulated signal A and modulated signalB. By this means, not only can the same kind of effect be obtained as inthe assignment examples shown in FIG. 15 and FIG. 16, but in addition,since assignment is performed to modulated signal A and modulated signalB alternately, a further effect can be achieved of being able to obtainspatial diversity gain.

In FIG. 19, data assignment is performed alternately to modulated signalA and modulated signal B. In this case, 6-bit data in which onlyodd-numbered items have been extracted, or 6-bit data in which onlyeven-numbered items have been extracted, is placed in symbols ofdifferent times. This is clear if, for example, data symbols (1), (3),(5), (6), (9), (11) of modulated signal A are looked at. By this means,not only can the same kind of effect be obtained as in the assignmentexamples shown in FIG. 15 and FIG. 16, but in addition, since assignmentis performed to modulated signal A and modulated signal B alternately, afurther effect can be achieved of being able to obtain spatial diversitygain.

In FIG. 20, data is first assigned to modulated signal A, and then datais assigned to modulated signal B. These are then assigned to symbols ofdifferent times, taking 6 bits after encoding as a unit. By this means,the same kind of effect can be obtained as in the assignment examplesshown in FIG. 15 and FIG. 16.

FIG. 21 shows the configuration of the signal processing section of amulti-antenna receiving apparatus that receives and demodulates signalstransmitted from multi-antenna transmitting apparatus 500 configured asshown in FIG. 17. The overall configuration of the multi-antennareceiving apparatus here may be as shown in FIG. 11, and signalprocessing section 311 may be configured as shown in FIG. 21.

Signal processing section 311 in FIG. 21, in which parts correspondingto those in FIG. 13 are assigned the same reference codes as in FIG. 13,has a similar configuration to signal processing section 311 in FIG. 13,differing only in having only one deinterleaving section 405 and onedecoder 407. Deinterleaving section 405 has modulated signal A softdecision value 404A and modulated signal B soft decision value 404B asinput, performs deinterleaving according to the frame configuration (thereverse of the processing performed by arranging(interleaving) section104 in FIG. 17), and obtains a post-deinterleaving soft decision value406. Decoder 407 has post-deinterleaving soft decision value 406 asinput, and obtains receive data 408 by decoding this post-deinterleavingsoft decision value 406.

Embodiment 3

In this embodiment, an actual mode is described for a case in which LDPCencoding is performed by a multi-antenna transmitting apparatus. Inaddition, an actual mode is described for a case in which adaptivemodulation is performed.

FIG. 22 is a drawing showing an example of assignment of post-encodingdata to data symbols by arranging(interleaving) sections 104A and 104Bwhen encoding sections 102A and 102B in FIG. 9 perform LDPC encodingwith respective post-encoding block sizes of 980 bits. In this case, 980bits in one encoded block are assigned to 980 modulated signal A symbolsA(1), A(2), . . . , A(980). Here, (1), (2), . . . , (980) indicate thedata order. Similarly, 980 bits in one encoded block are assigned to 980modulated signal B symbols B(1), B(2), . . . , B(980). Thus, data (bits)in one encoded block are assigned to a plurality of data symbols. Bythis means, burst errors can be suppressed more effectively than whendata in one encoded block is assigned to a small number of data symbols.

FIG. 23 is a drawing showing an example of assignment of post-encodingdata to data symbols by arranging(interleaving) section 104 whenencoding section 102 in FIG. 17 performs LDPC encoding with a block sizeof 980 bits. In this case, 980 bits in one encoded block are assigned to980 modulated signal A and modulated signal B symbols. Here, (1), (2), .. . , (980) indicate the data order. By assigning data (bits) in oneencoded block to a plurality of data symbols and a plurality of antennasin this way, burst errors can be suppressed more effectively than whendata in one encoded block is assigned to a small number of data symbols,and a further effect can also be achieved of being able to obtainspatial diversity gain.

Next, a mode will be described for a case in which the present inventionis applied to a multi-antenna transmitting apparatus that performsadaptive modulation (that is, switches the modulation method) accordingto the communication conditions.

FIG. 24 shows the configuration of a multi-antenna transmittingapparatus that performs adaptive modulation. Multi-antenna transmittingapparatus 600 in FIG. 24, in which parts corresponding to those in FIG.9 are assigned the same reference codes as in FIG. 9, is provided in abase station, for example. A receiving apparatus 2303 has a receivedsignal 2302 received by an antenna 2301 as input, performs receptionprocessing and obtains communication condition information transmittedby a communicating-party terminal (for example, information such as thebit error rate, packet error rate, frame error rate, received signalstrength, and multipath conditions), determines the modulation methodtherefrom, and outputs this as control information 2304. Frameconfiguration signal generation section 115 has control information 2304as input, determines the modulation method and frame configuration basedon control information 2304, and sends these to modulation sections 106Aand 106B, encoding sections 102A and 102B, and arranging(interleaving)sections 104A and 104B as frame configuration signal 116.

Arranging(interleaving) sections 104A and 104B change theirarrangement(interleaving) according to the modulation method in the sameway as described in Embodiment 1.

FIG. 25 shows an example of the configuration of a communicating-partyterminal that performs communication with multi-antenna transmittingapparatus 600. A transmitting apparatus 2403 of multi-antenna receivingapparatus 700 in FIG. 25, in which parts corresponding to those in FIG.11 are assigned the same reference codes as in FIG. 11, has transmitdata 2402, baseband signals 304_1 and 304_2, and receive data 312A and312B as input, and, for example, estimates the received signal strengthfrom baseband signals 304_1 and 304_2, finds the bit error rate, packeterror rate, and frame error rate from receive data 312A and 312B, formsa transmit signal 2404 containing these items of information andtransmit data, and outputs this as a radio wave from an antenna 2405. Bythis means, the modulation method of the base station (multi-antennatransmitting apparatus 600) is changed.

The method of changing the modulation method is not limited to this, anda similar effect can be achieved by having a communicating-partyterminal specify a desired modulation method, or having the base stationreceive a modulated signal transmitted from a communicating-partyterminal, and determine the modulation method of a modulated signal tobe transmitted based on the reception status of the received signal.

Embodiment 4

In this embodiment, a contrivance of the assignment method of last blockdata after LDPC encoding will be described. In FIG. 26, the verticalaxis indicates frequency, with data being transmitted using carriers 1through n, and the horizontal axis indicates time.

In FIG. 26, it is assumed that one packet of data is first transmittedusing 16 QAM. Therefore, four post-encoding blocks #1 through #4 aretransmitted in 980 symbols. Assuming that the quantity of one packet ofdata is variable, the amount of data transmitted last will notnecessarily be an amount that fills four encoded blocks in 16 QAM.

Thus, in this embodiment, if the number of encoded blocks transmittedlast is one, BPSK is selected as the modulation method of the lastblock, and only one encoded block, #1, is transmitted, as shown in FIG.26A.

If the number of encoded blocks transmitted last is more than one andnot more than two, QPSK is selected as the modulation method of the lastblocks, and two encoded blocks, #1 and #2, are transmitted, as shown inFIG. 26B. In this case, the kind of arrangement(interleaving) describedin FIG. 5B, FIG. 6B, FIG. 7B, or FIG. 8B may be performed.

If the number of encoded blocks transmitted last is more than two, 16QAM is selected as the modulation method of the last blocks, and fourencoded blocks, #1 through #4, are transmitted, as shown in FIG. 26C. Inthis case, the kind of arrangement(interleaving) described in FIG. 5C,FIG. 6C, FIG. 7C, or FIG. 8C may be performed.

By transmitting in this way, one encoded block of data is alwaystransmitted by means of 980 symbols, enabling the influence of fadingnotches to be reduced, and reception quality to be improved.

As another assignment method, 16 QAM may be selected regardless of thenumber of encoded blocks, and “0” dummy data, for example, may betransmitted for the entire deficient amount of data. With this kind oftransmission, one encoded block is still always transmitted by means of980 symbols, enabling the influence of fading notches to be reduced, andreception quality to be improved.

The above operations are extremely important in order to make receptionquality as uniform as possible when packet communication is performed.That is to say, if data of the last encoded block is transmitted asfewer than 980 symbols, the error rate performance of the last encodedblock will degrade, and the probability of packet error occurrence willincrease. The method described in this embodiment is effective inpreventing this.

Examples for Comparison

Using FIG. 27, conventionally commonly implemented assignment methodsand their drawbacks will now be described for comparison with the methodof uniformly assigning encoded block data to a plurality of symbolsaccording to the present invention.

FIG. 27A shows the received field strength state in a 980-symbolinterval as an example of the relationship between time and receivedfield strength as a communication condition.

FIG. 27B shows an example of a frame configuration when the modulationmethod is BPSK. As an example, FIG. 27B shows the case of a multicarriertransmission method that uses carrier 1 through carrier n, such as OFDMfor instance. Therefore, the vertical axis is the frequency axis, onwhich carriers 1 through n are represented. When the modulation methodis BPSK, 980 symbols are necessary to transmit one post-encoding block(block #1) as shown in FIG. 27B.

On the other hand, when the modulation method is 16 QAM, since 4 bitscan be transmitted in one symbol with 16 QAM, 245 symbols are necessaryto transmit one post-encoding block. Therefore, if 980 symbols are used,four blocks—block #1, block #2, block #3, and block #4—can betransmitted.

Conventionally, as with BPSK, the usual order of assignment in the timedirection is block #1 symbols, block #2 symbols, block #3 symbols, block#4 symbols, as shown in FIG. 27C.

In this case, when BPSK is used as in FIG. 27B, although there are timeswhen the received field strength is good and times when the receivedfield strength is poor for one encoded block even with the kind ofcommunication conditions in FIG. 27A, if decoding is performed inencoded block units, the possibility of errors being corrected throughthe influence of data with good received field strength is high.

On the other hand, when 16 QAM is used as in FIG. 27C, block #1 andblock #3 are located on the time axis at times when the received fieldstrength is good, and therefore exhibit good reception quality, whereasblock #2 and block #4 are located on the time axis at times when thereceived field strength is poor, and therefore exhibit poor receptionquality. As the number of symbols required by one encoded blockdecreases as the number of modulation multi-values of the modulationmethod increases in this way, the system is susceptible to the effectsof received field strength notches due to fading. That is to say, thesystem is susceptible to a fall in reception quality due to notches.

As explained in the above embodiments, a transmitting apparatus of thepresent invention effectively solves this problem without changing thecode length (block size).

Other Embodiments

In above Embodiment 1, the use of one encoding section 11 was taken as aprecondition in the description, but as a different embodiment, theabove embodiment can also be similarly implemented when the systemsupports a code with coding rate R=½ and ⅓ and a block size of 980 bits,as long as implementation is performed using coding rate R=½ and ⅓separately. Furthermore, the same kind of implementation as in the aboveembodiment can also be achieved when the system supports a code withcoding rate R=½ and ⅓ and block sizes of 980 and 1960 bits, as long asimplementation is performed separately in each case.

In above Embodiments 2 through 4, a case has been described of a MIMOsystem using spatial multiplexing in which a multi-antenna transmittingapparatus and multi-antenna receiving apparatus each have two antennas,but this is not a limitation, and similar implementation is alsopossible for a case in which the number of antennas is increased and thenumber of modulated signals transmitted is increased. Furthermore, thesame kind of effect can also be obtained when the present invention isapplied to a system using a spread spectrum communication method.

A multi-antenna transmitting apparatus of the present invention is notlimited to the configuration shown in Embodiment 2, and can also beapplied, for example, to a MIMO system using an eigenmode. An eigenmodecommunication method will now be described using FIG. 28.

In a MIMO system, when Channel State Information (CSI) is known not onlyon the receiving station side but on the transmitting station side, acommunication method can be implemented whereby the transmitting stationtransmits a signal vectored using a transmission channel signaturevector to the receiving station by means of a transmitting arrayantenna, and the receiving station detects and demodulates the transmitsignal using a reception channel signature vector associated with thetransmission channel signature vector from a receiving array antennareceived signal.

In particular, as a communication mode in which multiplex transmissionof signals composing a plurality of channels is performed in thecommunication space, there is an eigenmode that uses a channel matrixsingular vector or eigen vector. This eigenmode is a method that usesthis singular vector or eigenvector as an aforementioned channelsignature vector. Here, a channel matrix is a matrix that has complexchannel coefficients of a combination of each antenna element of thetransmitting array antenna and all or some of the antenna elements ofthe receiving array antenna as elements.

As a method whereby the transmitting station obtains downlink channelstate information, with TDD using carriers of the same frequency in aradio channel uplink and downlink, it is possible to perform estimatingor measuring of channel state information in the transmitting stationusing the uplink from the receiving station by means of channelreciprocity. On the other hand, with FDD using carriers of differentfrequencies in the uplink and downlink, accurate downlink CSI can beobtained by the transmitting apparatus by estimating or measuringdownlink channel state information in the receiving station andreporting the result to the transmitting station.

A characteristic of an eigenmode is that, particularly when a MIMOsystem radio channel can be handled as a narrow-band flat fadingprocess, MIMO system channel capacity can be maximized. For example, ina radio communication system that uses OFDM, it is usual for design tobe carried out so that guard intervals are inserted to eliminateinter-symbol interference due to multipath delayed waves, and OFDMsubcarriers are flat fading processes. Therefore, when an OFDM signal istransmitted in a MIMO system, using an eigenmode makes it possible, forexample, for a plurality of signals to be transmitted spatiallymultiplexed in each subcarrier.

As communication methods using a MIMO system, a number of methods havebeen proposed whereby, as opposed to an eigenmode in which downlinkchannel state information is assumed to be known in the transmittingstation and receiving station, channel state information for a radiochannel is known only in the receiving station. BLAST, for example, isknown as a method whereby signals are transmitted spatially multiplexedfor the same purpose as in an eigenmode. Also, transmission diversityusing a space time code, for example, is known as a method of obtainingan antenna space diversity effect at the sacrifice of the degree ofsignal multiplexing—that is, without increasing capacity. Whereas aneigenmode is a beam space mode in which a signal is transmitted vectoredfrom a transmitting array antenna—in other words, a signal istransmitted after being mapped in beam space—BLAST and space diversitycan be considered to be antenna element modes due to the fact that asignal is mapped onto an antenna element.

FIG. 28 shows examples of the configurations of an eigenmodecommunication transmitter and receiver. Based on channel stateinformation that is the result of estimation of the propagation channelbetween the transmitting station and receiving station, a transmissionchannel analysis section 2607 calculates a plurality of transmissionchannel signature vectors for composing a multiplex channel, and basinga channel matrix formed by means of the channel state information on SVD(Singular Value Decomposition), finds eigenvalues (for example, λA, λB,λC, . . . , λX), and eigen paths (for example, path A, path B, path C, .. . , path X), and outputs these as control information 2608.

In the transmitting station, a multiplex frame generation section 2601has a transmit digital signal and control information 2608 as input,generates a plurality of transmit frames for mapping onto multiplexchannels, and outputs a channel A transmit digital signal 2602A, channelB transmit digital signal 2602B, . . . , channel X transmit digitalsignal 2602X.

An encoding/arranging(interleaving)/modulation section 2603A has channelA transmit digital signal 2602A and control information 2608 as input,determines the coding rate and modulation method based on controlinformation 2608, and outputs a channel A baseband signal 2604A. Thesame kind of operations are also performed for channel B through channelX, and channel B baseband signal 2604B through channel X baseband signal2604X are obtained. To simplify the drawing, theencoding/arranging(interleaving)/modulation sections are shown as oneblock in FIG. 28, but in actuality, a configuration such as that inabove Embodiments 1 through 3 is used, and block encoded data isarranged(interleaved) so that encoded data within one block is assignedto a plurality of data symbols by an arranging(interleaving) section,and supplied to a modulation section.

A vector multiplexing section 2605 has channel A through channel Xbaseband signals 2604A through 2604X and control information 2608 asinput, multiplies channel A through channel X baseband signals 2604Athrough 2604X individually by a channel signature vector and performscombining, and then performs transmission to the receiving apparatusfrom a transmitting array antenna 2606.

In the receiving station, a reception channel analysis section 2615calculates in advance a plurality of reception channel signature vectorsfor separating multiplexed transmit signals based on channel stateinformation that is the result of estimation of the propagation channelbetween the transmitting station and receiving station. A multiplexsignal separation section 2610 has received signals received by areceiving array antenna 2609 as input, and generates a plurality ofreceived signals obtained by multiplying the channel signature vectorstogether—that is, a channel A received signal 2611A through channel Xreceived signal 2611X.

A decoding section 2612A has channel A received signal 2611A andtransmission method information 2618 as input, performs decoding basedon transmission method information 2618 (modulation method and codingrate information), and outputs a channel A digital signal 2613A. Thesame kind of operations are also performed for channel B through channelX, and channel B digital signal 2613B through channel X digital signal2613X are obtained.

A transmission method information detection section 2617 has channel Adigital signal 2613A ad input, extracts information on the transmittingmethod—for example, modulation method and coding rate—of each channel,and outputs transmission method information 2618.

A receive data combining section 2614 has channel A through channel Xdigital signals 2613A through 2613X and transmission method information2618 as input, and generates a receive digital signal.

The present application is based on Japanese Patent ApplicationNo.2005-198177 filed on Jul. 6, 2005, the entire content of which isexpressly incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The present invention has an effect of enabling burst errors to besuppressed with a comparatively simple configuration without changingthe block size of an encoded block even when the number of modulationmulti-values is increased, and is widely applicable to transmittingapparatuses and multi-antenna transmitting apparatuses that encodetransmit data using a block code such as an LDPC code, for example.

1. A transmitting apparatus comprising: an encoding section thatexecutes block encoding processing on transmission data comprising aplurality of bits to form blocks of block encoded data comprising theplurality of bits; an interleaving section that interleaves first bitsbelonging to the block encoded data such that one symbol is composed ofsecond bits each of which belongs to any one block of the blocks ofblock encoded data; a modulation section that outputs a baseband signalthat corresponds to the symbol, from the interleaved block encoded data;and a transmitting section that transmits a modulated signal that isbased on the baseband signal, wherein: the modulation section employs aplurality of modulation schemes; and the interleaving sectioninterleaves the first bits belonging to the block encoded data suchthat, even when an modulation scheme is employed, any two bitsarbitrarily extracted from the second bits forming the symbol belong todifferent blocks of the block encoded data.
 2. The transmittingapparatus according to claim 1, wherein the interleaving sectioninterleaves bits belonging to the blocks of block encoded data, theblocks of block encoded data being received as input from the encodingsection to the interleaving section consecutively in a time domain. 3.The transmitting apparatus according to claim 1, wherein the modulationsection employs a first modulation scheme and a second modulationscheme.
 4. The transmitting apparatus according to claim 3, wherein thefirst modulation scheme is quadrature phase shift keying and the secondmodulation scheme is 16 quadrature amplitude modulation.
 5. Thetransmitting apparatus according to claim 1, wherein: the modulationsection adaptively makes an M-ary number variable; and the interleavingsection interleaves the first bits belonging to the block encoded datasuch that the one symbol is comprised of bits each of which belong toany one of more of the blocks of block encoded data when the M-arynumber is larger.
 6. The transmitting apparatus according to claim 1,wherein the modulated signal is formed by employing an orthogonalfrequency division multiplexing scheme.
 7. A transmission methodcomprising: executing block encoding processing on transmission datacomprising a plurality of bits to form blocks of block encoded datacomprising the plurality of bits; interleaving first bits belonging tothe block encoded data such that one symbol is composed of second bitseach of which belongs to any one block of the blocks of block encodeddata; forming a baseband signal that corresponds to the symbol, from theinterleaved block encoded data; and transmitting a modulated signal thatis based on the baseband signal, wherein: a plurality of modulationschemes are employed; and the first bits belonging to the block encodeddata are interleaved such that, even when any modulation scheme isemployed, any two bits arbitrarily extracted from the second bitsforming the symbol belong to different blocks of the block encoded data.8. The transmission method according to claim 7, wherein theinterleaving is performed such that bits belonging to the blocks ofblock encoded data are interleaved, the blocks of block encoded databeing received as input consecutively in a time domain.
 9. Thetransmission method according to claim 7, wherein a first modulationscheme and a second modulation scheme are employed.
 10. The transmissionmethod according to claim 9, wherein the first modulation scheme isquadrature phase shift keying and the second modulation scheme is 16quadrature amplitude modulation.
 11. The transmission method accordingto claim 7, wherein: when the symbol is formed, an M-ary number isadaptively made variable; and the first bits belonging to the blockencoded data are interleaved such that the one symbol is comprised ofbits each of which belong to any one of more of the blocks of blockencoded data when the M-ary number is larger.
 12. The transmissionmethod according to claim 7, wherein the modulated signal is formed byemploying an orthogonal frequency division multiplexing scheme.